Caterpillar drive for conveyers



- 5, 1939- J. B. WEBB ET AL CATERPILLAR DRIVE FOR CONVEYSRS Fil'ed Dec.4, 1955 1 INVENTORSJ JE/FV/Sfi WEBB c 2 Sheets-Sheet 1 ATTORNEY.

3 1939- .J. B. WEBB ET AL 238,82 7 CATERPILLAR DRIVE FOR CDNVEYERS I IFiled Dec. 4, 1955 2 Sheets-Sheet 2 INVENTOR5.

ATTORNEY.

amt Aug. 8, 1939 UNITED, STATES PATENT OFFICE Grosse Pointe, Mich, WebbCompany, of Michigan assignors to Jervis B.

Detroit, Mich a corporation Application December 4, 1935, Serial No,52,804 2 Claims. (01. les -20's) This invention relates to driving unitsfor conveyer systems and is intended for use with conveyers of the typenow extensively operated in modern manufacturing plants for transport- Y5 mg articles during the process of manufacture.

An endless chain system, often of great length, carries the loads andmay be driven by one or more driving units. It is possible, but notalways practical, to use with these units what might be termed a directsprocket drive inwhlch the driving sprocket contacts directly with themain conveyer chain. This type of drive is best adapted for use wherethere is an opportunity to place the drive at a turn in the conveyersline of travel thereby to secure a larger number of sprocket teeth incontact with the conveyer chain.- But it is apparent that when such adrive is placed in a straight section of the conveyer chain, only asmall number of sprocket teeth will contact the chain at any one time, acondition which is obviously impractical.

- Another type of drive, better adapted for contacting straight sectionsof the conveyer chain, is termed a caterpillar drive, wherein a secondary endless driving chain having dogs extending from the links of thechain is set up to operate around two closely adjacent sprockets oneofwhich is driven. This driving unit is so placed relative to the mainconveyer chain that the 30 dog links engage the links of the conveyerchain and thereby drive the same. Obviously the length of the region ofcontact may be varied by the spacing of the two sprockets of thiscaterpillar drive and it is furthermore important with this type ofdrive to bring the caterpillar and main conveyer chains into and out ofdriving contact with a smoothness and positive action approaching thatof meshing gears. In previous practice, it has been found advantageousin providing smoother action, to set the caterpillar unit at a slightangle to the main conveyer chain. It is an object of the presentinvention however to improve the operation by providing a novelarrangement of guides to act with the conveyer chain and the caterpillarchain thereby to bring the two intodriving contact smoothly andpositively, hold this contact over a, sufliciently long region and thento effect a disengagement without jerking or other uneven 50 motion.Another phase of the problem is presented by the fact that main conveyerare necessarily of relatively large pitch and with a caterpillar chainand a main conveyen chain of the same pitch, the resulting caterpillarchain is oi much too large a pitch for efiicient operation. For if asuilicient number of sprocket teeth are to be kept in driving contactwith the caterpillar chain a large sprocket must be used; excessive itorque being placed upon the driving shaft of :5 said sprocket which notonly involves the use of very large diameter shafts to avoid breakagethereof, but also increases the load upon the unit and the consequenttorque required for driving it. If a caterpillar chain of smaller pitchcould be used, which would also mesh properly with,the large pitchconveyer-chain, it would enable a smaller more practical sized drivingsprocket to be used while having a suificient number of sprocket teethto contact with the links of the caterpillar chain, thus avoiding theincreased initial costs of the larger sprockets and shafts as well asother associated parts.- It is therefore a further object of theinvention to provide a driving unit with a caterpillar chain of a pitchwhich is smaller than thepitch of, the main conveyer chain but with arelation thereto such that the pitch of the main conveyer chain will bean even multiple of the pitch of the caterpillar chain, or twice thepitch of the main conveyer chain will be an even multiple of the pitchof the caterpiller chain, depending upon the type ofmain conveyer chainused.

The above and other objects of the invention will appear more. fullyfrom the following more detailed specification and by reference to theaccompanying drawings forming a part hereof and wherein: V

Fig. lis a plan view of one of the driving units constructed accordingto present invention; I

Fig. 2 is a side elevation of structure shown in Fig. 1;

' Fig. 3 is a section taken on the line 3-3 of Fig. 2 and shows in planview the caterpillar 40 drive and conveyer chain in contactingengagement as would be the case in an installation;

Fig. 4 is a section taken on the line 4-4 of Fig.

3 and shows the guides for the conveyer chain and caterpillar chain;

Fig. 5 is a view partly in section showing the details of one of the doglinks of the caterpillar chain.

Referring to Figs. 1 and 2, the reference character ill refers to thedriving unit generally which, as to some features thereof, is of thesame general'type' as described more in detail in the specification of aUnited States patent issued to Jervis B. Webb et al. March 1, 1932,entitled the principles ofv the "Equalizing drive for conveyer systemsNo. 1,847,152.

'Ihis driving unit i5 here used for illustration consists of a mainsupporting frame l5 which may be supported from the ceiling or anysuitable supportin structure. Mounted within the supporting frame i5 isa movable frame II with a plurality of bearing units such asanti-friction rollers i5 and i5 therebetween thereby allowing a limitedlongitudinal movement of the movable frame i'l upon the supporting framel5,,springs 25 and ii being provided between the frames i5 and I1normally to urge the frame l'l towards the ri ht in Fig. 1.

Mounted upon the movable frame i1 is a motor 22 which drives a speedchanging unit 25 also mounted on movable frame I'I from a pulley 24through a belt 55 to a pulley 25. The speed chang unit 25 may beof anysuitable type such as a well known, Reeves drive employing cone shapedpulleys 21, 25, 25, 55, such as described in the specification of mypatent mentioned above, wherein it is also explained that the Reevesdrive speed changing unit is adjustable by hand or may be so connectedwith the movable frame H as to be changed automatically depending uponthe amount of load thrown upon the unit to produce a longitudinalmovement of the frame I! against the springs 25, 2|. A pulley, orsprocket, 52 connected to the output shaft of the speed changing unit 25drives a pulley 55 on gear box 54 through a belt 35. The gear box 54 maycontain any suitable gearing so that the rotary motion of the shaft 55on which the pulley 53 is mounted will be transferred to the verticalshaft 51 on which is mounted a gear 55 which meshes with a large gear 55secured to a shaft 45 suitably mounted in bearings 4!, such shaft 45projecting downwardly through the frame i! as shown in Fig. 2 and havingsecured to its lower end a sprocket wheel 42.

Also on the lower side of the frame I! as shown in Fig. 2, there ismounted a depending bracket 45 with a projecting shaft 44 which forms abearing for an idler sprocket 45, free to rotate on the shaft 44 andrestrained against movement axially of said shaft between the bracket 45and a retaining member 45 secured to the shaft 44. As shown in Fig. 2,the sprockets 42 and 45 are aligned and a caterpillar chain 55 istrained around both sprockets 42 and 45, as seen best in Fig. 3, so thatwhen drive is applied by the motor 12 through the mechanism justdescribed, the sprocket 42 will continuously drive the chain 55 in aclockwise direction around sprockets 42 and 45.

Also extending downwardly from the movable frame l1 are four supportingstructural members 5|, 5!, 55 and 54. As shown in Fig. 3 the members 5|,52 have secured at their lower ends a guide rail 55 which is of suchwidth, as shown in Fig. 4, to form a backing or reaction support for therollers 55 in the chain links of the caterpillar chain 55. The guiderail 55 as also shownin Fig. 3 is formed with a radius at each end, theradius at the left hand end in Fig. 3 having its center designated asbeing smaller than the radius at the right hand end having itscenterdesignated as b. The guide rail 55 is straight between these two radiiand the shape thus provided causes the eaterpillar'chain to follow apath outwardly displaced from the straight line substantially tangent tothe pitch diameters of sprockets 42 and 45 which it would naturallyfollow. v

The supporting structural members 53 and 54 likewise support a guiderail 55 on the opposit n rmal travel and the side of the caterpillardrive which engages with the chain rollers 55 in a plane lyingsubstantially tangent to the pitch diameters of the sprockets 45 and 45.The mounting of the guide rail 55 also provides an adjustment to take upslack in the caterpillar chain 55, since the position of the said guiderail 55 maybe adjusted by change in the positions of nuts 55:: and 5511on threaded rod 550, a similar unit being provided at the support 54.

In order to insure continuous meshing engagement between the drivingcaterpillar chain and the conveyer chain there is also provided, asshown in Fig. 3, a supporting bracket 65 which may be secured to anystationary support and which bracket is provided with a plurality ofrollers 55 mounted for rotation and so spaced from the guide rail 55that there is a passage delined with just enough roomfor the mainconveyer chain 15 when meshed with the caterpillar drive chain 55 topass between the rollers 65 and the guide rail 55.

The caterpillar chain 55 ismade up of so-called dog links 15 which inthe particular example selected for illustration has connected betweenthem three intermediate plain links [5. As shown in Fig. there isprovided a roller 55 between the flanges of each of the links of thecaterpillar chain, said roller encircling thepins II which hold thelinks together. As before mentioned and shown best in Fig. 4, theflanges of each of the links proiect beyond the rollers 55 and extendbeyond each edge of the guide rail 55 thereby not only allowing therollers 55 to contact the vertical face of the guide rail and afford arolling contact therewith but said flanges also serve to maintain thechain rollers in proper alignment with said rail.

In order to further improve the engagement of the dog links of thecaterpillar chain with the main conveyer chain, the tooth contour atforward face 1,5 and rearward face 55 of the dog links I5 are designedwith a consideration of the path defined by the guide rail 55 relativeto the straight path ofthe main conveyer chain and a relation thereforeexists between the radii a and b at the ends of guide rail 55 and thetooth con tours at and 55.

Rollers 55, as shown best in Fig. 4, are approximately the same width asthe main conveyer chain 15 and provide rolling contact when said chainmoves against the rollers in passing between the guide rail 55 and therollerbracket.

The pitch of the caterpillar chain 55 is so selected that it is smallerthan the pitch of the main conveyer chain 15, the relation being someeven multiple of the pitch of the caterpillar chain 55. That is, asshown in Fig. 3, the pitch of the chain I5 is twice the pitch of thechain 55 and three intermediate plain links 15 are provided between eachpair of dog links '15. In this way, the dog links engage every otherlink of the conveyer chain I5 and the caterpillar chain 55 is broken upinto a relatively greater number of links than would be the case if thepitches of both chains were the'same.

With these conditions, it is possible to reduce thesizeofthesprocketsfland sincethe same number of teeth in driving contact can be had in amuchsmaller sprocket than would be available in a relatively largersprocket using a chain of the larger pitch.

' In operation, the bracket is so placed as to rest against the conveyerchain 15 in its line of driving unit I5 is so located that the face ofthe guide rail 55 is spaced from the roller 66 and bracket 55 a distancejust suificient to allow space for caterpillar chain 50 and mainconveyer chain 10 when the dog links of chain 50 are in driving meshwith the links of conveyer chain 10. It is to be noted that as thecaterpillar chain 50 moves clockwise as shown in Fig. 3 around sprockets42 and 45 and as a dog link comes in' contact with the left hand end ofthe guide rail 55, as shown in Fig. 3, the radius on said guide railcauses the said link 15 to move in a path such that it graduallyapproaches contact with the conveyer chain 10. The radius shown withcenter a on the guiderail 55 is so selected that the link 75 is inefiect turned relative to the chain 10 so that when the forward face I9contacts the chain 10,,

' right hand end of the guide rail shown at b in Fig. 3, the path issuch that as the link traverses this radius it turns upon the face incontact with the conveyer chain 10 and gradually disengages therefromwith a partial rolling effect until it is entirelydisengaged and passesaround the sprocket 42. veyer chain backed by the rollers 66 and thecaterpillar links positively guided for engaging and disengaging withthe chain will greatly improve the drive over one in which a straightcaterpillar chain is used with no guide or other backing for theconveyer chain, or when a fiat guide without rollers is used.

The particular constructional assemblies herein disclosed have beenselected merely as illustrative of the principles of the invention andnot as limiting the invention to the specific details selected forillustration. It will, therefore, be understood that many changes,.variations and modifications may be resorted to without departing fromsuch principles, for example, the assembly shown in Fig. 3 is notlimited to a floating drive such as shown in Figs. 1 and 2.

The main conveyer chain"), as shown, is the so-called Wilmot type chain,which is disclosed in Wilmot United States Patent No. 870,704. It is ofcourse understood that other types of chain may be used.

It is also noted that the showing in Fig. 3 may be varied as to the typeof chain and the pitch of such chain, always considering that therelation in pitch between the caterpillar chain and the main drivingchain must be such as to allow meshing for driving engagement whilepreferably keeping the caterpillar chain pitch smaller than the pitch ofthe main conveyer chain. Furthermore, if alternate main conveyer chainlinks are to be engaged as in the so-called Wilmot chain shown, thentwice the pitch of the main conveyer chain must be an even multiple ofthe pitch of the caterpillar chain so that dog links will always come inproper location. When dif- :terent pitch combinations are used there mayIt is apparent that the con-- of course be a difl'erent number of plainlinks between dog links ofthe caterpillar chain but if the abovementioned relation is maintained meshing will always be possible. It isalso apparent that a type of chain might be used such that each link ofthe conveyer chain could be engaged by a dog link and ,then the relationwould be such that the pitch of the conveyer chain be an even multipleof the pitch of the caterpillar chain. It is also possible to select acombination such as actually shown in Fig. 3 wherein the pitch of themain conveyer chain is an even multiple of the pitch of the caterpillarchain but with dog links meshing with every other link of the mainconveyer chain. In this instance, however, the statement that twice the"pitch of the conveyer chain is an even multiple of the pitch of thecaterpillar chain is also true.

A general statement covering the above, as well as other possiblecombinations, would be that the pitch distance between links of theconveyor chain which are engaged by dog links must be some even multipleof the pitch of the caterpillar chain while maintaining the pitch of themain conveyer chain greater than the pitch of the caterpillar chain.

We claim:

1. In a driving unit for a main conveyer chain of the type wherein anendless caterpillar chain having projecting toothed driving links iscarried around two adjacent sprockets so positioned as to efiect adriving contact between said endless caterpillar chain and said mainconveyer chain, characterized by an arcuate shaped guide I rail todefine the path of said caterpillar'chain in a region adjacent said mainconveyer chain to effect approach and recession to and from drivingcontact with said chain, and guide means comprising a plurality ofrollers positioned on one side of said main conveyer-chain and so spacedfrom said guide rail as to retain said caterpillar chain and said mainconveyer chain between said guide rail and said roller guide meansthereby to require a definite relative.

path of movement for said main driving chain and said caterpillardriving chain.

2. In a'driving unit for a main conveyer chain oi the type wherein acaterpillar driving chain is operated around two adjacent sprockets,said chain being provided with toothed projections of substantiallyinvolute contour for driving contact with said main conveyer chain,characterized by the fact that the pitch of said caterpillar chain isless than but an even multiple of the pitch of said main conveyer chain,a guide rail defining a definite path for said caterpillar chain guidemeans comprising a plurality of rollers spaced from said guide rail fordefining the path of said main conveyer chain and retaining saidcaterpillar chain and said main conveyer chain between said guide railand said roller guide means, the said guide rail and said roller guidemeans being of such shape and position relative to the shape andposition of'said toothed pro- Jections oi involute contour on ,saidcaterpillar chain whereby a smooth rolling driving engagement anddisengagement of said toothed projections of said caterpillar chain withsaid main conveyer chain is effected.

JERVIS, B. WEBB. NORMAN H. PREBLE.

